On 09.12.14 13:45, Daniel Feist wrote:
> Hi,
>
> I believe I fully understanding the use of IOStrategies when using
> Grizzly as a Http Server, and am currently using the
> WorkerThreadIOStrategy given that handling of http requests will not
> be non-blocking in my scenario. It is also clear that with this
> strategy a worker thread will be used to handle READ and CLOSE
> IOEvents, but not ACCEPT events. This all makes sense.
>
> That said, I'm slightly confused about the role of IOStrategies in
> Client scenarios, particularly with the WorkerThreadIOStrategy:
>
> - From examples I see that client implementations typically call
> ctx.write to send the http request within an CompletionHandler after
> asycronously establishing a connection.
> - With this approach the kernal thread pool is used for the async
> connection, but is also then used to perform the ctx.write including
> HttpFilter processing etc. (this is because WorkerThreadIOStrategy
> only provides threadpool for READ/CLOSE events).
> - When the response is recieved from the remote server, this is a READ
> event, and so the WorkerThreadIOStrategy provides workers such that
> each response is handed off to a worker thread before HttpFilter is
> processed.
>
> What seems strange about this when using:
>
> i) Why does sending of request occurs in selector thread and not a
> worker thread when WorkerThreadIOStrategy is being used?
It is initiated by user, so Grizzly just sends the message in whatever
thread picked by user.
> ii) There appears to be a mismatch between use of worker thread for
> response processing but not request processing and I'm unsure why if
> there is only a limited number of selectors sending requests (say 4),
> I'd want a thread pool of (say up to 200) workers to handle responses.
In general, if we know the code is not blocking - we suggest to not do
or do as less as possible thread-context switches.
The asymmetry may be explained by the fact, that writing we perform is
non-blocking, but response processing might be blocking and we don't
want to block Selector thread.
Thanks.
WBR,
Alexey.